This is BLADE 4mm Serrated Titanium Nut (4).
The new BLADE serrated titanium nut is designed for all 1/10 Touring car wheel nuts. The BLADE nut is built by CNC from a 6/4 Titanium raw bar, the serrated surface can bite. The wheel surface tight without any chance of loose during the race, the BLADE nut weigh only 0.65g each,4 pcs/pack.